Russia's big bargaining chip in this conflict is natural gas.
NY Times reports that they have used their gas and oil resources for coercion before.
Russia supplies most of the natural gas that Europe uses, and a lot of it travels by pipeline through Ukraine. So not only does Ukraine depend on Russian natural gas, but Europe depends on the Ukraine route. Russia has a good hand if they like to play a tough game (and they do).
You may remember that America has been
producing natural gas at a tremendous rate and has huge resources. There is a movement to urge the U.S. government to approve exporting it - to Ukraine as our first customer, and without delay - because it would surprise no one if
Russia played the energy card to control events.
In addition to potential help for Ukraine, see
Time U.S. for another way American natural gas is playing a part in foreign policy.